How do you calculate inset and overlay door sizes?
Measure the clear opening at several positions and check the frame for square. Enter the dimensions your project will use. Overlay is the amount a finished door extends beyond the opening; inset reveal is the gap between an inset front and its surrounding opening. They describe different geometry.
Full and partial overlay use the entered coverage. A partial-overlay label does not itself divide a measurement by two. Adjacent cabinets, hinge arms and mounting plates can constrain the coverage you can actually achieve.
Single overlay: W = Ow + L + R; H = Oh + T + B
Paired overlay, each: W = (Ow + L + R − G) / 2
Single inset: W = Ow − 2I; H = Oh − 2I
Paired inset, each: W = (Ow − 2I − G) / 2
Direct per-door scope: W and H are the entered dimensions of each door.
Direct overall-pair scope: each W = (entered overall width − G) / 2; H = entered height.Recalculate the same opening with different arrangements
These are arithmetic examples, not a hardware recommendation: opening 21 × 27 inches; overlays 1/2 inch per outside edge; inset perimeter reveal 1/8 inch; center gap 1/8 inch except where stated. Every millimeter value is calculated from the same inch value using 25.4 mm per inch.
Direct mode has an explicit size scope. Per-door scope makes two copies of the entered dimensions when two doors are selected. Overall-pair scope treats the entered width as the combined outside span, subtracts the center gap and divides by two. Choose the scope that matches your measurement; do not apply opening overlays or inset reveals again.
| Arrangement | Each door: width × height | Calculation condition |
|---|---|---|
| Single overlay | 22″ (558.8 mm) × 28″ (711.2 mm) | Opening + left/right or top/bottom overlays |
| Two overlay doors — each | 10 15/16″ (277.8125 mm) × 28″ (711.2 mm) | Subtract the actual center gap once, then divide width by two |
| Single inset | 20 3/4″ (527.05 mm) × 26 3/4″ (679.45 mm) | Subtract two perimeter reveals from each opening dimension |
| Two inset doors — each | 10 5/16″ (261.9375 mm) × 26 3/4″ (679.45 mm) | Subtract left reveal, right reveal and the actual center gap |
| Two inset doors, 1/4″ center gap — each | 10 1/4″ (260.35 mm) × 26 3/4″ (679.45 mm) | A changed center gap changes the result |
| Direct per-door size, one or two doors — each | 21″ (533.4 mm) × 27″ (685.8 mm) | Per-door scope: entered width and height describe each finished door |
| Direct overall pair span — each | 10 7/16″ (265.1125 mm) × 27″ (685.8 mm) | Overall scope: subtract the center gap from the entered combined span, then divide by two |
Keep the center gap independent of the perimeter reveal
A paired opening has a left reveal, a right reveal and a separate gap between the two doors. Only when all three happen to match can the expression be shortened to “opening width minus three equal gaps.” Changing the center-gap input must change each door width by half that change.
For example, increasing the center gap from 1/8 to 1/4 inch reduces each inset door width by 1/16 inch. The table above makes that difference visible. A 1/8 inch input is a planning example, not a universal minimum swing clearance. Confirm the actual reveal and opening motion with the selected hinge and project requirements.
Door geometry comes before hinge selection
The calculator can place a cup center from an edge distance. It cannot obtain the compatible mounting-plate height, opening clearance or achievable overlay from geometry alone. Use the exact hinge, mounting method and plate drawing.
AWI’s casework requirements distinguish hinge-dependent reveal overlay from the inset face-frame detail. Do not treat a single number from one detail as the required reveal for every cabinet, material and grade. Retain the project’s agreed dimensions and test the actual opening motion.
- Record the finished size of each front, its quantity and the center gap.
- Check hinge-side clearance, neighboring fronts, handles and internal hardware.
- Carry the door size into the cut list; size the frame and panel from the finished door, not directly from the opening.
Frequently asked questions
What is the formula for two inset cabinet doors?
Each width is (opening width − 2 × perimeter reveal − center gap) / 2. Height is opening height − 2 × perimeter reveal. The center gap is independent of the perimeter reveal and is subtracted once before dividing.
Does direct finished size describe one door or the whole pair?
Choose the explicit scope. Per-door scope describes each finished door and selecting two duplicates that size. Overall-pair scope describes the combined outside width; the calculator subtracts the center gap and divides by two. Neither applies opening overlays or inset reveals.
Is a 1/8 inch reveal required for every inset door?
No. It is an editable example. Project requirements, hinge motion, material and the applicable construction detail determine the needed reveal. Check the selected hardware and the actual cabinet.
Does half overlay mean the calculator halves my overlay?
No. Enter the actual coverage required at each edge. The arrangement label does not derive a hardware overlay or mounting-plate height.
Can I carry my opening and frame inputs to the other tools?
Yes. Calculation links retain supported dimensions, including ow, oh, overlay, stile and groove. Values in shared URLs use decimal inches; the unit setting controls display. Inspect inherited inputs before using the next result.
Sources and scope
- AWI 0641 Architectural Wood Casework — section 3.4 aesthetic requirements
Reveal overlay depends on hinge clearance; panel construction must allow movement. The inset face-frame detail has project- and grade-specific dimensions; it is not a universal reveal preset.
- Blum CLIP top BLUMOTION 110° brochure — drilling diagram, printed page 4
71B3550, 71B3650 and 71B3750 reference family: 35 mm cup, minimum 13 mm boring depth, B = 3–7 mm. Other variants need their own drawing.
Worked examples are calculations under the stated assumptions. They are not physical test results or manufacturer approval of a finished assembly.